Conventional digital imaging devices or cameras often include a lens assembly (which includes multiple lens elements) that focuses image light onto an image sensor that measures the image light and generates an image based on the measurements. FIG. 1 illustrates a common configuration for a digital imaging device 100, which includes an image sensor 110 and a lens assembly 115 including multiple lens elements 120. Lens assembly 115 is disposed over image sensor 110 to focus image light 125 from an object onto the pixels of image sensor 110. Lens assembly 115 may include convex and/or concave lens elements 120 that together give lens assembly 115 an effective focal length (“EFL”). The lens assembly 115 also provides a certain Depth of Field (“DOF”). DOF refers to the range of distances in the field of view of an image sensor that appear to be well focused in an image captured by image sensor 110. The Field of View (“FOV”) of lens assembly 115 refers to the angular extent that is viewable through lens assembly 115 at a given moment.
Lens assembly 115 has a z-axis height H1, which is also referred to as the optical total track length (“TTL”). The optical TTL is typically influenced by the FOV and the size of image sensor 110, as well as other design choices. A larger optical TTL may limit the applications or uses of digital imaging device 100 because of space constraints. Therefore, a lens assembly that allows a digital imaging device to capture high resolution images with a large FOV while reducing the optical TTL can be advantageous. A lens assembly that provides a large DOF where both far and near images are brought into focus is also desirable.